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The Population Biology of the Genus Viola: I. The Demography of Viola Sororia

O. T. Solbrig, Sandra J. Newell and D. T. Kincaid
Journal of Ecology
Vol. 68, No. 2 (Jul., 1980), pp. 521-546
DOI: 10.2307/2259420
Stable URL: http://www.jstor.org/stable/2259420
Page Count: 26
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The Population Biology of the Genus Viola: I. The Demography of Viola Sororia
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Abstract

(1) A census of all plants of Viola sororia 1-yr-old or older was carried out at regular intervals over an 8-yr period in a forest site in New England. Over a 2-yr period seedlings were similarly recorded, and each leaf and reproductive structure on twenty selected plants was marked and its fate recorded at weekly intervals. (2) Calculations were made of population flux, age distribution, survivorship and life expectancy of 1-yr-old or older plants, and of seedlings. (3) Fluctuation in population size was small compared to the number of individual plants gained and lost in the population. There was a remarkably constant annual death risk, superimposed upon a seasonal cycle, May-September being a period of greater mortality than the winter months when the plants were inactive. (4) The life expectancy of a 1-yr-old plant was over 10 yr. While seedlings and adult plants exhibited a Deevey type-III mortality curve, leaves had a Deevey type-I curve. (5) It was also established that seedling survival and production-probability are a function of plant size; the relationship is exponential in the case of seed production. It is suggested that individual plant size is regulated by competition for environmental resources.

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